GSoC node tool

(bzr r8846.2.1)

1 files changed, 965 insertions, 0 deletions

diff --git a/src/ui/tool/node.cpp b/src/ui/tool/node.cpp
new file mode 100644
index 000000000..5f792cfc7
--- /dev/null
+++ b/src/ui/tool/node.cpp
@@ -0,0 +1,965 @@
+/** @file
+ * Editable node - implementation
+ */
+/* Authors:
+ *   Krzysztof Kosiński <tweenk.pl@gmail.com>
+ *
+ * Copyright (C) 2009 Authors
+ * Released under GNU GPL, read the file 'COPYING' for more information
+ */
+
+#include <iostream>
+#include <stdexcept>
+#include <boost/utility.hpp>
+#include <glib.h>
+#include <glib/gi18n.h>
+#include <2geom/transforms.h>
+#include "ui/tool/event-utils.h"
+#include "ui/tool/node.h"
+#include "display/sp-ctrlline.h"
+#include "display/sp-canvas.h"
+#include "display/sp-canvas-util.h"
+#include "desktop.h"
+#include "desktop-handles.h"
+#include "preferences.h"
+#include "sp-metrics.h"
+#include "sp-namedview.h"
+
+namespace Inkscape {
+namespace UI {   
+
+static SelectableControlPoint::ColorSet node_colors = {
+    {
+        {0xbfbfbf00, 0x000000ff}, // normal fill, stroke
+        {0xff000000, 0x000000ff}, // mouseover fill, stroke
+        {0xff000000, 0x000000ff}  // clicked fill, stroke
+    },
+    {0x0000ffff, 0x000000ff}, // normal fill, stroke when selected
+    {0xff000000, 0x000000ff}, // mouseover fill, stroke when selected
+    {0xff000000, 0x000000ff}  // clicked fill, stroke when selected
+};
+
+static ControlPoint::ColorSet handle_colors = {
+    {0xffffffff, 0x000000ff}, // normal fill, stroke
+    {0xff000000, 0x000000ff}, // mouseover fill, stroke
+    {0xff000000, 0x000000ff}  // clicked fill, stroke
+};
+
+std::ostream &operator<<(std::ostream &out, NodeType type)
+{
+    switch(type) {
+    case NODE_CUSP: out << 'c'; break;
+    case NODE_SMOOTH: out << 's'; break;
+    case NODE_AUTO: out << 'a'; break;
+    case NODE_SYMMETRIC: out << 'z'; break;
+    default: out << 'b'; break;
+    }
+    return out;
+}
+
+/** Computes an unit vector of the direction from first to second control point */
+static Geom::Point direction(Geom::Point const &first, Geom::Point const &second) {
+    return Geom::unit_vector(second - first);
+}
+
+/**
+ * @class Handle
+ * Represents a control point of a cubic Bezier curve in a path.
+ */
+
+double Handle::_saved_length = 0.0;
+bool Handle::_drag_out = false;
+
+Handle::Handle(NodeSharedData const &data, Geom::Point const &initial_pos, Node *parent)
+    : ControlPoint(data.desktop, initial_pos, Gtk::ANCHOR_CENTER, SP_CTRL_SHAPE_CIRCLE, 7.0,
+        &handle_colors, data.handle_group)
+    , _parent(parent)
+    , _degenerate(true)
+{
+    _cset = &handle_colors;
+    _handle_line = sp_canvas_item_new(data.handle_line_group, SP_TYPE_CTRLLINE, NULL);
+    setVisible(false);
+    signal_grabbed.connect(
+        sigc::bind_return(
+            sigc::hide(
+                sigc::mem_fun(*this, &Handle::_grabbedHandler)),
+            false));
+    signal_dragged.connect(
+        sigc::hide<0>(
+            sigc::mem_fun(*this, &Handle::_draggedHandler)));
+    signal_ungrabbed.connect(
+        sigc::hide(sigc::mem_fun(*this, &Handle::_ungrabbedHandler)));
+}
+Handle::~Handle()
+{
+    sp_canvas_item_hide(_handle_line);
+    gtk_object_destroy(GTK_OBJECT(_handle_line));
+}
+
+void Handle::setVisible(bool v)
+{
+    ControlPoint::setVisible(v);
+    if (v) sp_canvas_item_show(_handle_line);
+    else sp_canvas_item_hide(_handle_line);
+}
+
+void Handle::move(Geom::Point const &new_pos)
+{
+    Handle *other, *towards, *towards_second;
+    Node *node_towards; // node in direction of this handle
+    Node *node_away; // node in the opposite direction
+    if (this == &_parent->_front) {
+        other = &_parent->_back;
+        node_towards = _parent->_next();
+        node_away = _parent->_prev();
+        towards = node_towards ? &node_towards->_back : 0;
+        towards_second = node_towards ? &node_towards->_front : 0;
+    } else {
+        other = &_parent->_front;
+        node_towards = _parent->_prev();
+        node_away = _parent->_next();
+        towards = node_towards ? &node_towards->_front : 0;
+        towards_second = node_towards ? &node_towards->_back : 0;
+    }
+
+    if (Geom::are_near(new_pos, _parent->position())) {
+        // The handle becomes degenerate. If the segment between it and the node
+        // in its direction becomes linear and there are smooth nodes
+        // at its ends, make their handles colinear with the segment
+        if (towards && towards->isDegenerate()) {
+            if (node_towards->type() == NODE_SMOOTH) {
+                towards_second->setDirection(*_parent, *node_towards);
+            }
+            if (_parent->type() == NODE_SMOOTH) {
+                other->setDirection(*node_towards, *_parent);
+            }
+        }
+        setPosition(new_pos);
+        return;
+    }
+
+    if (_parent->type() == NODE_SMOOTH && Node::_is_line_segment(_parent, node_away)) {
+        // restrict movement to the line joining the nodes
+        Geom::Point direction = _parent->position() - node_away->position();
+        Geom::Point delta = new_pos - _parent->position();
+        // project the relative position on the direction line
+        Geom::Point new_delta = (Geom::dot(delta, direction)
+            / Geom::L2sq(direction)) * direction;
+        setRelativePos(new_delta);
+        return;
+    }
+
+    switch (_parent->type()) {
+    case NODE_AUTO:
+        _parent->setType(NODE_SMOOTH, false);
+        // fall through - auto nodes degrade into smooth nodes
+    case NODE_SMOOTH: {
+        /* for smooth nodes, we need to rotate the other handle so that it's colinear
+         * with the dragged one while conserving length. */
+        other->setDirection(new_pos, *_parent);
+        } break;
+    case NODE_SYMMETRIC:
+        // for symmetric nodes, place the other handle on the opposite side
+        other->setRelativePos(-(new_pos - _parent->position()));
+        break;
+    default: break;
+    }
+
+    setPosition(new_pos);
+}
+
+void Handle::setPosition(Geom::Point const &p)
+{
+    ControlPoint::setPosition(p);
+    sp_ctrlline_set_coords(SP_CTRLLINE(_handle_line), _parent->position(), position());
+
+    // update degeneration info and visibility
+    if (Geom::are_near(position(), _parent->position()))
+        _degenerate = true;
+    else _degenerate = false;
+    if (_parent->_handles_shown && _parent->visible() && !_degenerate) {
+        setVisible(true);
+    } else {
+        setVisible(false);
+    }
+    // If both handles become degenerate, convert to parent cusp node
+    if (_parent->isDegenerate()) {
+        _parent->setType(NODE_CUSP, false);
+    }
+}
+
+void Handle::setLength(double len)
+{
+    if (isDegenerate()) return;
+    Geom::Point dir = Geom::unit_vector(relativePos());
+    setRelativePos(dir * len);
+}
+
+void Handle::retract()
+{
+    setPosition(_parent->position());
+}
+
+void Handle::setDirection(Geom::Point const &from, Geom::Point const &to)
+{
+    setDirection(to - from);
+}
+
+void Handle::setDirection(Geom::Point const &dir)
+{
+    Geom::Point unitdir = Geom::unit_vector(dir);
+    setRelativePos(unitdir * length());
+}
+
+char const *Handle::handle_type_to_localized_string(NodeType type)
+{
+    switch(type) {
+    case NODE_CUSP: return _("Cusp node handle");
+    case NODE_SMOOTH: return _("Smooth node handle");
+    case NODE_SYMMETRIC: return _("Symmetric node handle");
+    case NODE_AUTO: return _("Auto-smooth node handle");
+    default: return "";
+    }
+}
+
+void Handle::_grabbedHandler()
+{
+    _saved_length = _drag_out ? 0 : length();
+}
+
+void Handle::_draggedHandler(Geom::Point &new_pos, GdkEventMotion *event)
+{
+    Geom::Point parent_pos = _parent->position();
+    // with Alt, preserve length
+    if (held_alt(*event)) {
+        new_pos = parent_pos + Geom::unit_vector(new_pos - parent_pos) * _saved_length;
+    }
+    // with Ctrl, constrain to M_PI/rotationsnapsperpi increments.
+    if (held_control(*event)) {
+        Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+        int snaps = 2 * prefs->getIntLimited("/options/rotationsnapsperpi/value", 12, 1, 1000);
+        Geom::Point origin = _last_drag_origin();
+        Geom::Point rel_origin = origin - parent_pos;
+        new_pos = parent_pos + Geom::constrain_angle(Geom::Point(0,0), new_pos - parent_pos, snaps,
+            _drag_out ? Geom::Point(1,0) : Geom::unit_vector(rel_origin));
+    }
+    signal_update.emit();
+}
+
+void Handle::_ungrabbedHandler()
+{
+    // hide the handle if it's less than dragtolerance away from the node
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    int drag_tolerance = prefs->getIntLimited("/options/dragtolerance/value", 0, 0, 100);
+    
+    Geom::Point dist = _desktop->d2w(_parent->position()) - _desktop->d2w(position());
+    if (dist.length() <= drag_tolerance) {
+        move(_parent->position());
+    }
+    _drag_out = false;
+}
+
+static double snap_increment_degrees() {
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    int snaps = prefs->getIntLimited("/options/rotationsnapsperpi/value", 12, 1, 1000);
+    return 180.0 / snaps;
+}
+
+Glib::ustring Handle::_getTip(unsigned state)
+{
+    if (state_held_alt(state)) {
+        if (state_held_control(state)) {
+            return format_tip(C_("Path handle tip",
+                "<b>Ctrl+Alt</b>: preserve length and snap rotation angle to %f° increments"),
+                snap_increment_degrees());
+        } else {
+            return C_("Path handle tip",
+                "<b>Alt:</b> preserve handle length while dragging");
+        }
+    } else {
+        if (state_held_control(state)) {
+            return format_tip(C_("Path handle tip",
+                "<b>Ctrl:</b> snap rotation angle to %f° increments, click to retract"),
+                snap_increment_degrees());
+        }
+    }
+    switch (_parent->type()) {
+    case NODE_AUTO:
+        return C_("Path handle tip",
+            "<b>Auto node handle:</b> drag to convert to smooth node");
+    default:
+        return format_tip(C_("Path handle tip", "<b>%s:</b> drag to shape the curve"),
+            handle_type_to_localized_string(_parent->type()));
+    }
+}
+
+Glib::ustring Handle::_getDragTip(GdkEventMotion *event)
+{
+    Geom::Point dist = position() - _last_drag_origin();
+    // report angle in mathematical convention
+    double angle = Geom::angle_between(Geom::Point(-1,0), position() - _parent->position());
+    angle += M_PI; // angle is (-M_PI...M_PI] - offset by +pi and scale to 0...360
+    angle *= 360.0 / (2 * M_PI);
+    GString *x = SP_PX_TO_METRIC_STRING(dist[Geom::X], _desktop->namedview->getDefaultMetric());
+    GString *y = SP_PX_TO_METRIC_STRING(dist[Geom::Y], _desktop->namedview->getDefaultMetric());
+    GString *len = SP_PX_TO_METRIC_STRING(length(), _desktop->namedview->getDefaultMetric());
+    Glib::ustring ret = format_tip(C_("Path handle tip",
+        "Move by %s, %s; angle %.2f°, length %s"), x->str, y->str, angle, len->str);
+    g_string_free(x, TRUE);
+    g_string_free(y, TRUE);
+    g_string_free(len, TRUE);
+    return ret;
+}
+
+/**
+ * @class Node
+ * Represents a curve endpoint in an editable path.
+ */
+
+Node::Node(NodeSharedData const &data, Geom::Point const &initial_pos)
+    : SelectableControlPoint(data.desktop, initial_pos, Gtk::ANCHOR_CENTER,
+        SP_CTRL_SHAPE_DIAMOND, 9.0, *data.selection, &node_colors, data.node_group)
+    , _front(data, initial_pos, this)
+    , _back(data, initial_pos, this)
+    , _type(NODE_CUSP)
+    , _handles_shown(false)
+{
+    // NOTE we do not set type here, because the handles are still degenerate
+    // connect to own grabbed signal - dragging out handles
+    signal_grabbed.connect(
+        sigc::mem_fun(*this, &Node::_grabbedHandler));
+    signal_dragged.connect( sigc::hide<0>(
+        sigc::mem_fun(*this, &Node::_draggedHandler)));
+}
+
+// NOTE: not using iterators won't make this much quicker because iterators can be 100% inlined.
+Node *Node::_next()
+{
+    NodeList::iterator n = NodeList::get_iterator(this).next();
+    if (n) return n.ptr();
+    return NULL;
+}
+Node *Node::_prev()
+{
+    NodeList::iterator p = NodeList::get_iterator(this).prev();
+    if (p) return p.ptr();
+    return NULL;
+}
+
+void Node::move(Geom::Point const &new_pos)
+{
+    // move handles when the node moves.
+    Geom::Point old_pos = position();
+    Geom::Point delta = new_pos - position();
+    setPosition(new_pos);
+    _front.setPosition(_front.position() + delta);
+    _back.setPosition(_back.position() + delta);
+
+    // if the node has a smooth handle after a line segment, it should be kept colinear
+    // with the segment
+    _fixNeighbors(old_pos, new_pos);
+}
+
+void Node::transform(Geom::Matrix const &m)
+{
+    Geom::Point old_pos = position();
+    setPosition(position() * m);
+    _front.setPosition(_front.position() * m);
+    _back.setPosition(_back.position() * m);
+
+    /* Affine transforms keep handle invariants for smooth and symmetric nodes,
+     * but smooth nodes at ends of linear segments and auto nodes need special treatment */
+    _fixNeighbors(old_pos, position());
+}
+
+Geom::Rect Node::bounds()
+{
+    Geom::Rect b(position(), position());
+    b.expandTo(_front.position());
+    b.expandTo(_back.position());
+    return b;
+}
+
+void Node::_fixNeighbors(Geom::Point const &old_pos, Geom::Point const &new_pos)
+{
+    /* This method restores handle invariants for neighboring nodes,
+     * and invariants that are based on positions of those nodes for this one. */
+    
+    /* Fix auto handles */
+    if (_type == NODE_AUTO) _updateAutoHandles();
+    if (old_pos != new_pos) {
+        if (_next() && _next()->_type == NODE_AUTO) _next()->_updateAutoHandles();
+        if (_prev() && _prev()->_type == NODE_AUTO) _prev()->_updateAutoHandles();
+    }
+    
+    /* Fix smooth handles at the ends of linear segments.
+     * Rotate the appropriate handle to be colinear with the segment.
+     * If there is a smooth node at the other end of the segment, rotate it too. */
+    Handle *handle, *other_handle;
+    Node *other;
+    if (_is_line_segment(this, _next())) {
+        handle = &_back;
+        other = _next();
+        other_handle = &_next()->_front;
+    } else if (_is_line_segment(_prev(), this)) {
+        handle = &_front;
+        other = _prev();
+        other_handle = &_prev()->_back;
+    } else return;
+
+    if (_type == NODE_SMOOTH && !handle->isDegenerate()) {
+        handle->setDirection(other->position(), new_pos);
+        /*Geom::Point handle_delta = handle->position() - position();
+        Geom::Point new_delta = Geom::unit_vector(new_direction) * handle_delta.length();
+        handle->setPosition(position() + new_delta);*/
+    }
+    // also update the handle on the other end of the segment
+    if (other->_type == NODE_SMOOTH && !other_handle->isDegenerate()) {
+        other_handle->setDirection(new_pos, other->position());
+        /*
+        Geom::Point handle_delta2 = other_handle->position() - other->position();
+        Geom::Point new_delta2 = Geom::unit_vector(new_direction) * handle_delta2.length();
+        other_handle->setPosition(other->position() + new_delta2);*/
+    }
+}
+
+void Node::_updateAutoHandles()
+{
+    // Recompute the position of automatic handles.
+    if (!_prev() || !_next()) {
+        _front.retract();
+        _back.retract();
+        return;
+    }
+    // TODO describe in detail what the code below does
+    Geom::Point vec_next = _next()->position() - position();
+    Geom::Point vec_prev = _prev()->position() - position();
+    double len_next = vec_next.length(), len_prev = vec_prev.length();
+    if (len_next > 0 && len_prev > 0) {
+        Geom::Point dir = Geom::unit_vector((len_prev / len_next) * vec_next - vec_prev);
+        _back.setRelativePos(-dir * (len_prev / 3));
+        _front.setRelativePos(dir * (len_next / 3));
+    } else {
+        _front.retract();
+        _back.retract();
+    }
+}
+
+void Node::showHandles(bool v)
+{
+    _handles_shown = v;
+    if (!_front.isDegenerate()) _front.setVisible(v);
+    if (!_back.isDegenerate()) _back.setVisible(v);
+}
+
+/** Sets the node type and optionally restores the invariants associated with the given type.
+ * @param type The type to set
+ * @param update_handles Whether to restore invariants associated with the given type.
+ *                       Passing false is useful e.g. wen initially creating the path,
+ *                       and when making cusp nodes during some node algorithms.
+ *                       Pass true when used in response to an UI node type button.
+ */
+void Node::setType(NodeType type, bool update_handles)
+{
+    if (type == NODE_PICK_BEST) {
+        pickBestType();
+        updateState(); // The size of the control might have changed
+        return;
+    }
+
+    // if update_handles is true, adjust handle positions to match the node type
+    // handle degenerate handles appropriately
+    if (update_handles) {
+        switch (type) {
+        case NODE_CUSP:
+            // if the existing type is also NODE_CUSP, retract handles
+            if (_type == NODE_CUSP) {
+                _front.retract();
+                _back.retract();
+            }
+            break;
+        case NODE_AUTO:
+            // auto handles make no sense for endnodes
+            if (isEndNode()) return;
+            _updateAutoHandles();
+            break;
+        case NODE_SMOOTH: {
+            // rotate handles to be colinear
+            // for degenerate nodes set positions like auto handles
+            bool prev_line = _is_line_segment(_prev(), this);
+            bool next_line = _is_line_segment(this, _next());
+            if (isDegenerate()) {
+                _updateAutoHandles();
+            } else if (_front.isDegenerate()) {
+                // if the front handle is degenerate and this...next is a line segment,
+                // make back colinear; otherwise pull out the other handle
+                // to 1/3 of distance to prev
+                if (next_line) {
+                    _back.setDirection(*_next(), *this);
+                } else if (_prev()) {
+                    Geom::Point dir = direction(_back, *this);
+                    _front.setRelativePos((_prev()->position() - position()).length() / 3 * dir);
+                }
+            } else if (_back.isDegenerate()) {
+                if (prev_line) {
+                    _front.setDirection(*_prev(), *this);
+                } else if (_next()) {
+                    Geom::Point dir = direction(_front, *this);
+                    _back.setRelativePos((_next()->position() - position()).length() / 3 * dir);
+                }
+            } else {
+                // both handles are extended. make colinear while keeping length
+                // first make back colinear with the vector front ---> back,
+                // then make front colinear with back ---> node
+                // (not back ---> front because back's position was changed in the first call)
+                _back.setDirection(_front, _back);
+                _front.setDirection(_back, *this);
+            }
+            } break;
+        case NODE_SYMMETRIC:
+            if (isEndNode()) return; // symmetric handles make no sense for endnodes
+            if (isDegenerate()) {
+                // similar to auto handles but set the same length for both
+                Geom::Point vec_next = _next()->position() - position();
+                Geom::Point vec_prev = _prev()->position() - position();
+                double len_next = vec_next.length(), len_prev = vec_prev.length();
+                double len = (len_next + len_prev) / 6; // take 1/3 of average
+                if (len == 0) return;
+                
+                Geom::Point dir = Geom::unit_vector((len_prev / len_next) * vec_next - vec_prev);
+                _back.setRelativePos(-dir * len);
+                _front.setRelativePos(dir * len);
+            } else {
+                // Both handles are extended. Compute average length, use direction from
+                // back handle to front handle. This also works correctly for degenerates
+                double len = (_front.length() + _back.length()) / 2;
+                Geom::Point dir = direction(_back, _front);
+                _front.setRelativePos(dir * len);
+                _back.setRelativePos(-dir * len);
+            }
+            break;
+        default: break;
+        }
+    }
+    _type = type;
+    _setShape(_node_type_to_shape(type));
+    updateState();
+}
+
+void Node::pickBestType()
+{
+    _type = NODE_CUSP;
+    bool front_degen = _front.isDegenerate();
+    bool back_degen = _back.isDegenerate();
+    bool both_degen = front_degen && back_degen;
+    bool neither_degen = !front_degen && !back_degen;
+    do {
+        // if both handles are degenerate, do nothing
+        if (both_degen) break;
+        // if neither are degenerate, check their respective positions
+        if (neither_degen) {
+            Geom::Point front_delta = _front.position() - position();
+            Geom::Point back_delta = _back.position() - position();
+            // for now do not automatically make nodes symmetric, it can be annoying
+            /*if (Geom::are_near(front_delta, -back_delta)) {
+                _type = NODE_SYMMETRIC;
+                break;
+            }*/
+            if (Geom::are_near(Geom::unit_vector(front_delta),
+                Geom::unit_vector(-back_delta)))
+            {
+                _type = NODE_SMOOTH;
+                break;
+            }
+        }
+        // check whether the handle aligns with the previous line segment.
+        // we know that if front is degenerate, back isn't, because
+        // both_degen was false
+        if (front_degen && _next() && _next()->_back.isDegenerate()) {
+            Geom::Point segment_delta = Geom::unit_vector(_next()->position() - position());
+            Geom::Point handle_delta = Geom::unit_vector(_back.position() - position());
+            if (Geom::are_near(segment_delta, -handle_delta)) {
+                _type = NODE_SMOOTH;
+                break;
+            }
+        } else if (back_degen && _prev() && _prev()->_front.isDegenerate()) {
+            Geom::Point segment_delta = Geom::unit_vector(_prev()->position() - position());
+            Geom::Point handle_delta = Geom::unit_vector(_front.position() - position());
+            if (Geom::are_near(segment_delta, -handle_delta)) {
+                _type = NODE_SMOOTH;
+                break;
+            }
+        }
+    } while (false);
+    _setShape(_node_type_to_shape(_type));
+    updateState();
+}
+
+bool Node::isEndNode()
+{
+    return !_prev() || !_next();
+}
+
+/** Move the node to the bottom of its canvas group. Useful for node break, to ensure that
+ * the selected nodes are above the unselected ones. */
+void Node::sink()
+{
+    sp_canvas_item_move_to_z(_canvas_item, 0);
+}
+
+NodeType Node::parse_nodetype(char x)
+{
+    switch (x) {
+    case 'a': return NODE_AUTO;
+    case 'c': return NODE_CUSP;
+    case 's': return NODE_SMOOTH;
+    case 'z': return NODE_SYMMETRIC;
+    default: return NODE_PICK_BEST;
+    }
+}
+
+void Node::_setState(State state)
+{
+    // change node size to match type and selection state
+    switch (_type) {
+    case NODE_AUTO:
+    case NODE_CUSP:
+        if (selected()) _setSize(11);
+        else _setSize(9);
+        break;
+    default:
+        if(selected()) _setSize(9);
+        else _setSize(7);
+        break;
+    }
+    SelectableControlPoint::_setState(state);
+}
+
+bool Node::_grabbedHandler(GdkEventMotion *event)
+{
+    // dragging out handles
+    if (!held_shift(*event)) return false;
+
+    Handle *h;
+    Geom::Point evp = event_point(*event);
+    Geom::Point rel_evp = evp - _last_click_event_point();
+
+    // this should work even if dragtolerance is zero and evp coincides with node position
+    double angle_next = HUGE_VAL;
+    double angle_prev = HUGE_VAL;
+    bool has_degenerate = false;
+    // determine which handle to drag out based on degeneration and the direction of drag
+    if (_front.isDegenerate() && _next()) {
+        Geom::Point next_relpos = _desktop->d2w(_next()->position())
+            - _desktop->d2w(position());
+        angle_next = fabs(Geom::angle_between(rel_evp, next_relpos));
+        has_degenerate = true;
+    }
+    if (_back.isDegenerate() && _prev()) {
+        Geom::Point prev_relpos = _desktop->d2w(_prev()->position())
+            - _desktop->d2w(position());
+        angle_prev = fabs(Geom::angle_between(rel_evp, prev_relpos));
+        has_degenerate = true;
+    }
+    if (!has_degenerate) return false;
+    h = angle_next < angle_prev ? &_front : &_back;
+
+    h->setPosition(_desktop->w2d(evp));
+    h->setVisible(true);
+    h->transferGrab(this, event);
+    Handle::_drag_out = true;
+    return true;
+}
+
+void Node::_draggedHandler(Geom::Point &new_pos, GdkEventMotion *event)
+{
+    if (!held_control(*event)) return;
+    if (held_alt(*event)) {
+        // with Ctrl+Alt, constrain to handle lines
+        // project the new position onto a handle line that is closer
+        Geom::Point origin = _last_drag_origin();
+        Geom::Line line_front(origin, origin + _front.relativePos());
+        Geom::Line line_back(origin, origin + _back.relativePos());
+        double dist_front, dist_back;
+        dist_front = Geom::distance(new_pos, line_front);
+        dist_back = Geom::distance(new_pos, line_back);
+        if (dist_front < dist_back) {
+            new_pos = Geom::projection(new_pos, line_front);
+        } else {
+            new_pos = Geom::projection(new_pos, line_back);
+        }
+    } else {
+        // with Ctrl, constrain to axes
+        // TODO this probably has to be separated into an AxisConstrainablePoint class
+        // TODO maybe add diagonals when the distance from origin is large enough?
+        Geom::Point origin = _last_drag_origin();
+        Geom::Point delta = new_pos - origin;
+        Geom::Dim2 d = (fabs(delta[Geom::X]) < fabs(delta[Geom::Y])) ? Geom::X : Geom::Y;
+        new_pos[d] = origin[d];
+    }
+}
+
+Glib::ustring Node::_getTip(unsigned state)
+{
+    if (state_held_shift(state)) {
+        if ((_next() && _front.isDegenerate()) || (_prev() && _back.isDegenerate())) {
+            if (state_held_control(state)) {
+                return format_tip(C_("Path node tip",
+                    "<b>Shift+Ctrl:</b> drag out a handle and snap its angle "
+                    "to %f° increments"), snap_increment_degrees());
+            }
+            return C_("Path node tip",
+                "<b>Shift:</b> drag out a handle, click to toggle selection");
+        }
+        return C_("Path node statusbar tip", "<b>Shift:</b> click to toggle selection");
+    }
+
+    if (state_held_control(state)) {
+        if (state_held_alt(state)) {
+            return C_("Path node tip", "<b>Ctrl+Alt:</b> move along handle lines");
+        }
+        return C_("Path node tip",
+            "<b>Ctrl:</b> move along axes, click to change node type");
+    }
+    
+    // assemble tip from node name
+    char const *nodetype = node_type_to_localized_string(_type);
+    return format_tip(C_("Path node tip",
+        "<b>%s:</b> drag to shape the path, click to select this node"), nodetype);
+}
+
+Glib::ustring Node::_getDragTip(GdkEventMotion *event)
+{
+    Geom::Point dist = position() - _last_drag_origin();
+    GString *x = SP_PX_TO_METRIC_STRING(dist[Geom::X], _desktop->namedview->getDefaultMetric());
+    GString *y = SP_PX_TO_METRIC_STRING(dist[Geom::Y], _desktop->namedview->getDefaultMetric());
+    Glib::ustring ret = format_tip(C_("Path node statusbar tip", "Move by %s, %s"),
+        x->str, y->str);
+    g_string_free(x, TRUE);
+    g_string_free(y, TRUE);
+    return ret;
+}
+
+char const *Node::node_type_to_localized_string(NodeType type)
+{
+    switch (type) {
+    case NODE_CUSP: return _("Cusp node");
+    case NODE_SMOOTH: return _("Smooth node");
+    case NODE_SYMMETRIC: return _("Symmetric node");
+    case NODE_AUTO: return _("Auto-smooth node");
+    default: return "";
+    }
+}
+
+/** Determine whether two nodes are joined by a linear segment. */
+bool Node::_is_line_segment(Node *first, Node *second)
+{
+    if (!first || !second) return false;
+    if (first->_next() == second)
+        return first->_front.isDegenerate() && second->_back.isDegenerate();
+    if (second->_next() == first)
+        return second->_front.isDegenerate() && first->_back.isDegenerate();
+    return false;
+}
+
+SPCtrlShapeType Node::_node_type_to_shape(NodeType type)
+{
+    switch(type) {
+    case NODE_CUSP: return SP_CTRL_SHAPE_DIAMOND;
+    case NODE_SMOOTH: return SP_CTRL_SHAPE_SQUARE;
+    case NODE_AUTO: return SP_CTRL_SHAPE_CIRCLE;
+    case NODE_SYMMETRIC: return SP_CTRL_SHAPE_SQUARE;
+    default: return SP_CTRL_SHAPE_DIAMOND;
+    }
+}
+
+
+/**
+ * @class NodeList
+ * @brief An editable list of nodes representing a subpath.
+ *
+ * It can optionally be cyclic to represent a closed path.
+ * The list has iterators that act like plain node iterators, but can also be used
+ * to obtain shared pointers to nodes.
+ *
+ * @todo Manage geometric representation to improve speed
+ */
+
+NodeList::NodeList(SubpathList &splist)
+    : _list(splist)
+    , _closed(false)
+{
+    this->list = this;
+    this->next = this;
+    this->prev = this;
+}
+
+NodeList::~NodeList()
+{
+    clear();
+}
+
+bool NodeList::empty()
+{
+    return next == this;
+}
+
+NodeList::size_type NodeList::size()
+{
+    size_type sz = 0;
+    for (ListNode *ln = next; ln != this; ln = ln->next) ++sz;
+    return sz;
+}
+
+bool NodeList::closed()
+{
+    return _closed;
+}
+
+/** A subpath is degenerate if it has no segments - either one node in an open path
+ * or no nodes in a closed path */
+bool NodeList::degenerate()
+{
+    return closed() ? empty() : ++begin() == end();
+}
+
+NodeList::iterator NodeList::before(double t, double *fracpart)
+{
+    double intpart;
+    *fracpart = std::modf(t, &intpart);
+    int index = intpart;
+
+    iterator ret = begin();
+    std::advance(ret, index);
+    return ret;
+}
+
+// insert a node before i
+NodeList::iterator NodeList::insert(iterator i, Node *x)
+{
+    ListNode *ins = i._node;
+    x->next = ins;
+    x->prev = ins->prev;
+    ins->prev->next = x;
+    ins->prev = x;
+    x->ListNode::list = this;
+    _list.signal_insert_node.emit(x);
+    return iterator(x);
+}
+
+void NodeList::splice(iterator pos, NodeList &list)
+{
+    splice(pos, list, list.begin(), list.end());
+}
+
+void NodeList::splice(iterator pos, NodeList &list, iterator i)
+{
+    NodeList::iterator j = i;
+    ++j;
+    splice(pos, list, i, j);
+}
+
+void NodeList::splice(iterator pos, NodeList &list, iterator first, iterator last)
+{
+    ListNode *ins_beg = first._node, *ins_end = last._node, *at = pos._node;
+    for (ListNode *ln = ins_beg; ln != ins_end; ln = ln->next) {
+        list._list.signal_remove_node.emit(static_cast<Node*>(ln));
+        ln->list = this;
+        _list.signal_insert_node.emit(static_cast<Node*>(ln));
+    }
+    ins_beg->prev->next = ins_end;
+    ins_end->prev->next = at;
+    at->prev->next = ins_beg;
+
+    ListNode *atprev = at->prev;
+    at->prev = ins_end->prev;
+    ins_end->prev = ins_beg->prev;
+    ins_beg->prev = atprev;
+}
+
+void NodeList::shift(int n)
+{
+    // 1. make the list perfectly cyclic
+    next->prev = prev;
+    prev->next = next;
+    // 2. find new begin
+    ListNode *new_begin = next;
+    if (n > 0) {
+        for (; n > 0; --n) new_begin = new_begin->next;
+    } else {
+        for (; n < 0; ++n) new_begin = new_begin->prev;
+    }
+    // 3. relink begin to list
+    next = new_begin;
+    prev = new_begin->prev;
+    new_begin->prev->next = this;
+    new_begin->prev = this;
+}
+
+void NodeList::reverse()
+{
+    for (ListNode *ln = next; ln != this; ln = ln->prev) {
+        std::swap(ln->next, ln->prev);
+        Node *node = static_cast<Node*>(ln);
+        Geom::Point save_pos = node->front()->position();
+        node->front()->setPosition(node->back()->position());
+        node->back()->setPosition(save_pos);
+    }
+    std::swap(next, prev);
+}
+
+void NodeList::clear()
+{
+    for (iterator i = begin(); i != end();) erase (i++);
+}
+
+NodeList::iterator NodeList::erase(iterator i)
+{
+    // some acrobatics are required to ensure that the node is valid when deleted;
+    // otherwise the code that updates handle visibility will break
+    Node *rm = static_cast<Node*>(i._node);
+    ListNode *rmnext = rm->next, *rmprev = rm->prev;
+    ++i;
+    _list.signal_remove_node.emit(rm);
+    delete rm;
+    rmprev->next = rmnext;
+    rmnext->prev = rmprev;
+    return i;
+}
+
+void NodeList::kill()
+{
+    for (SubpathList::iterator i = _list.begin(); i != _list.end(); ++i) {
+        if (i->get() == this) {
+            _list.erase(i);
+            return;
+        }
+    }
+}
+
+NodeList &NodeList::get(Node *n) {
+    return *(n->list());
+}
+NodeList &NodeList::get(iterator const &i) {
+    return *(i._node->list);
+}
+
+
+/**
+ * @class SubpathList
+ * @brief Editable path composed of one or more subpaths
+ */
+
+} // namespace UI
+} // namespace Inkscape
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :